Texture looking streched/low quality

Ive been working on my map the dev textures look ok and then i decided to start texturing to find that all the texture i applyed were all streched or low quality if anyone knows how to fix this all help is apprishiated thanks

Most likely you had texture lock on the whole time you were working, so every time you resized something, the texture got stretched or squashed along with it. Generally speaking, you want to keep that off except when you're resizing overlays. As for the "low quality", Hammer naturally has lower texture detail than the game (unless you have textures turned down in the game as well); don't worry about that.